This invention relates to apparatus for data transfer with a rotating data storage disk, particularly a flexible magnetic disk, which is normally packaged in cartridge form. More particularly, the invention pertains to a system for saving power unnecessarily consumed by one or more of various standard components of such rotating disk data storage apparatus.
Various power saving schemes have been suggested and used with floppy disk drives. Among such conventional suggestions is that described and claimed in U.S. Pat. No. 4,658,307 filed by Tsuyuguchi et al. and assigned to the assignee of the instant application. Tsuyuguchi et al. teaches to connect the disk motor drive circuit, the head motor drive circuit, and the read/write circuit, all standard components of the disk drive, to a power supply via a power saving switch. This switch is closed only when the floppy disk cartridge is loaded in the disk drive, or when the "drive select" and "motor on" signals from the host system, under which control the disk drive operates, are in prescribed states. The motor drive circuits and read/write circuit are therefore not powered in the absence of the disk cartridge, or when the "drive select" and "motor on" signals are in other than the prescribed states, even if the complete data processing system, comprising the host and one or more disk drives, is powered on. A very substantial saving of power can thus be accomplished.
There are, however, various other power consuming components in the disk drive that were conventionally held powered even when the disk drive was standing by, that is, when no data transfer operation is in progress in the disk drive. Such power consuming components include a supply voltage detector circuit for detecting whether the supply voltage has built up to a predetermined value when the system is switched on, a file protect sensor for sensing whether the loaded disk cartridge is protected against erasure or writing, a disk capacity sensor for discriminating between one-megabyte and two-megabyte disk cartridges which may be loaded interchangeably in the disk dive, and another disk capacity sensor for discriminating between four-megabyte and other capacity disks cartridges.
In exploring the possibilities of further reducing the waste of power by disk drives, the applicant has paid attention to the information which is contained in control data from some host systems and which indicates whether the disk drive is standing by. This information will be hereinafter referred to as the power save signal as it has proved to lend itself for use for power saving purposes. As far as the applicant is aware, however, there has yet been developed no disk drive that utilizes the power save signal for saving power.
The applicant has therefore manufactured an experimental disk drive that becomes powered and unpowered in response to the power save signal. No appreciable saving of power has resulted, however. This is because the power save signal goes high and low at inconveniently short intervals, and the transducer is recalibrated on Track Zero, the reference track, on the disk each time the disk drive becomes powered in response to the power save signal. Transducer recalibration is a very power consuming operation and is unnecessary if the host is held informed of the current transducer position on the disk.